Performance evaluation and DFT study of a room temperature methylamine gas sensor based on QCM with Fe3O4-PVAc nanofiber active layer

The negative impact of methylamine gas, which has the potential to harm the environment and human health, necessitates reliable sensors capable of detecting it at room temperature. The research developed a methylamine gas sensor based on a quartz crystal microbalance (QCM) with an active layer of polyvinyl acetate (PVAc) nanofibers and surface-modified with Fe3O4. PVAc nanofiber was fabricated using the electrospinning method, and then deposited with Fe₃O₄ using the dropcasting method. The PVAc nanofibers exhibited a smooth and continuous morphology and did not undergo damage after Fe₃O₄ deposition. The detection of Fe mass in the deposited nanofiber also confirmed the success of Fe₃O₄ addition. The sensor with Fe₃O₄ showed a significantly higher response to methylamine (51.5 Hz at 120 ppm) compared to the PVAc sensor (29.5 Hz at 120 ppm). The sensor also exhibits a high sensitivity of 0.442 Hz·ppm⁻¹ with a limit of detection of 9.2 ppm. In addition, Fe₃O₄ also accelerates the response and recovery times, while maintaining good selectivity and long-term stability. Furthermore, the density functional theory (DFT) calculations reveal stable adsorption energy, notable charge transfer, and short adsorption distances between methylamine and the Fe₃O₄ surface through Fe–N bonds. These findings indicate the strong gas-surface interaction, which is well-aligned with experimental results. This study demonstrates that the fabricated sensor exhibits reliable performance and has great potential as a room temperature methylamine gas sensor with high sensitivity and selectivity.